| 1. |
- Assefa, Anteneh, 1983-
(författare)
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Tracing and apportioning sources of dioxins using multivariate pattern recognition techniques
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- High levels of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) in edible fish in the Baltic Sea have raised health concerns in the Baltic region and the rest of Europe. Thus, there are urgent needs to characterize sources in order to formulate effective mitigation strategies. The aim of this thesis is to contribute to a better understanding of past and present sources of PCDD/Fs in the Baltic Sea environment by exploring chemical fingerprints in sediments, air, and biota. The spatial and temporal patterns of PCDD/F distributions in the Baltic Sea during the 20th century were studied in Swedish coastal and offshore sediment cores. The results showed that PCDD/F levels peaked in 1975 (± 7 years) in coastal and 1991 (± 5 years) in offshore areas. The time trends of PCDD/Fs in the sediment cores also showed that environmental half-lives of these pollutants have been shorter in coastal than in offshore areas (15 ± 5 and 29 ± 14 years, respectively). Consequently, there have been remarkable recoveries in coastal areas, but slower recovery in offshore areas with 81 ± 12% and 38 ± 11% reductions from peak levels, respectively.Source-to-receptor multivariate modeling by Positive Matrix Factorization (PMF) showed that six types of PCDD/F sources are and have been important for the Baltic Sea environment: PCDD/Fs related to i) atmospheric background, ii) thermal processes, iii) manufacture and use of tetra-chlorophenol (TCP) and iv) penta-chlorophenol (PCP), v) industrial use of elementary chlo- rine and the chloralkali-process (Chl), and vi) hexa-CDD sources. The results showed that diffuse sources (i and ii) have consistently contributed >80% of the total amounts in the Southern Baltic Sea. In the Northern Baltic Sea, where the biota is most heavily contaminated, impacts of local sources (TCP, PCP and Chl) have been higher, contributing ca. 50% of total amounts. Among the six sources, only Thermal and chlorophenols (ii-iv) have had major impacts on biota. The impact of thermal sources has, however, been declining as shown from source apportioned time-trend data of PCDD/Fs in Baltic herring. In contrast, impacts of chlorophenol-associated sources generally increased, remained at steady-state or slowly decreased during 1990-2010, suggesting that these sources have substantially contributed to the persistently high levels of PCDD/Fs in Baltic biota.Atmospheric sources of PCDD/Fs for the Baltic region (Northern Europe) were also investigated, and specifically whether the inclusion of parallel measurements of metals in the analysis of air would help back-tracking sources. PCDD/Fs and metals in high-volume air samples from a rural field station near the shore of the central Baltic Sea were measured. The study focused on the winter season and air from the S and E sectors, as these samples showed elevated levels of PCDD/Fs, particularly PCDFs. Several metals were found to correlate significantly with the PCDFs. The wide range of candidate metals as source markers for PCDD/F emissions, and the lack of an up-to-date extensive compilation of source characteristics for metal emission from vari- ous sources, limited the use of the metals as source markers. The study was not able to pin-point primary PCDD/F sources for Baltic air, but it demonstrated a new promising approach for source tracing of air emissions. The best leads for back-tracking primary sources of atmospheric PCDD/Fs in Baltic air were seasonal trends and PCDD/F congener patterns, pointing at non-industrial related thermal sources related to heating. The non-localized natures of the sources raise challenges for managing the emissions and thus societal efforts are required to better control atmospheric emissions of PCDD/Fs.
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| 2. |
- Shanmugam, Kavitha, 1992-
(författare)
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Circularity Assessment of Water and Waste in Cities : A Proposed Framework for Sustainable Performance Evaluation using LCA and LCC
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Urbanization is a global phenomenon, happening on a massive scale and at a rapid rate, with 68% of the planet’s population predicted to be living in cities by 2050 (UN-DESA, 2018). The sustainability of a city (Goal 11 of UN SDGs) undergoing rapid urbanization depends on its ability to maintain a low consumption of resources and materials at any given time (referred to as the urban metabolic rate), whilst simultaneously providing essential municipal services to its inhabitants, such as a water supply, wastewater treatment and solid waste management. The latter must comply with circular economy principles, meaning recovery of byproducts, prevention of discharge of toxic pollutants, and avoidance of landfill usage. The appended papers in the thesis (Papers I–V) describe sustainable assessments of wastewater and waste services to increase their degree of circularity, using tools such as Life Cycle Assessment (LCA) and Life Cycle Costing (LCC). Paper I describes the environmental performance of using the biogas from a Wastewater Treatment Plant (WWTP) and converting it to Liquefied Biomethane (LBM), which can used as fuel in Tractor-Trailers (TT). Overall, the study suggests that changing from diesel to LBM fuel improves the environmental performance of TT. However, the magnitude of environmental benefit depends on an alternate source of electricity required for operation of the WWTP. Paper II evaluates the Social Cost-Benefit Analysis (SCBA) of Compressed Biomethane (CBM) obtained from a food waste digestion plant in Mumbai, India for use as a fuel in transit buses. SCBA results indicate that the food waste-based CBM model can save 6.86 billion Indian rupees (99.4 million USD) annually for Mumbai. Paper III describes the Sustainable Return on Investment (SROI) of lightweight Advanced High Strength Steel (AHSS) and Carbon Fiber Reinforced Polymer (CFRP) intensive multi-material Body in White (BIW) for automobiles. The SROI of CFRP BIWs is maximized when carbon fiber production uses energy from a low carbon-intensity electric grid or decentralized sources such as waste-to-energy incineration plants. Paper IV assesses the ecoefficiency of a thermal insulation panel that consists of a Polyurethane (PU) foam core sandwiched between two epoxy composite skins, prepared by reinforcing Glass Fibers (GF) and SFA (Silanized Fly Ash) in epoxy resin. The results revealed that the ecoefficiency of the composite panels is positive (47%) and superior to that of market incumbent alternatives with PU foam or rockwool cores and steel skins. Paper V quantifies the Total Cost to Society (TCS) (sum of private cost and environmental externalities cost) of a centralized urban WWTP, including the operation as well as byproduct utilization stream. The environmental performance and circular compliance are both factored in, when determining the TCS of a WWTP. The results revealed savings of 1.064 million USD, which include direct and indirect revenues to the plant, as well as avoidance costs attributed to environmental externalities. Based on the studies described in4these papers, a five-stage assessment framework for determining the overall sustainability performance of essential treatment services in a city is proposed in this thesis. The framework considers the combined effect of urban metabolic features and initiatives aimed at improving circular compliance of essential services.
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| 3. |
- Wang, Dong, 1987-
(författare)
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How can data science contribute to a greener world? : an exploration featuring machine learning and data mining for environmental facilities and energy end users
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Human society has taken many measures to address environmental issues. For example, deploying wastewater treatment plants (WWTPs) to alleviate water pollution and the shortage of usable water; using waste-to-energy (WtE) plants to recover energy from the waste and reduce its environmental impact. However, managing these facilities is taxing because the processes and operations are always complex and dynamic. These characteristics hinder the comprehensive and precise understanding of the processes through the conventional mechanistic models. On the other hand, with the development of the Fourth Industrial Revolution, large-volume and high-resolution data from automatic online monitoring have become increasingly obtainable. These data usually reflect abundant detailed information of process activities that can be utilized for optimizing process control. Similarly, data monitoring is also adopted by the resource end users. For example, energy consumption is usually recorded by commercial buildings for optimizing energy consumption behavior, eventually saving running costs and reducing carbon footprint. With the data recorded and retrieved, appropriate data science methods need to be employed to extract the desired information. Data science is a field incorporating formulating data-driven solutions, data preprocessing, analyzing data with particular algorithms, and employing results to support high-level decisions in various application scenarios.The aim of this PhD project is to explore how data science can contribute to a more sustainable world from the perspectives of both improving the operation of environmental engineering processes and optimizing the activities of energy end users. The major work and corresponding results are as follows:(1) (Paper I) An ML workflow consisting of Random Forest (RF) models, Deep Neural Network (DNN) models, Variable Importance Measure (VIM) analyses, and Partial Dependence Plot (PDP) analyses was developed and utilized to model WWTP processes and reveal how operational features impact on effluent quality. The case study was conducted on a full-scale WWTP in Sweden with large data (105,763 samples). This paper was the first ML application study investigating cause-and-effect relationships for full-scale WWTPs. Also, for the first time, time lags between process parameters were treated rigorously for accurate information uncovering. The cause-and-effect findings in this paper can contribute to more sophisticated process control that is more precise and cost-effective. (2) (Paper II) An upgraded workflow was designed to enhance the WWTP cause-and-effect investigation to be more precise, reliable, and comprehensive. Besides RF, two more typical tree-based models, XGBoost and LightGBM, were introduced. Also, two more metrics were adopted for a more comprehensive performance evaluation. A unified and more advanced interpretation method, SHapley Additive exPlanations (SHAP), was employed to aid model comparison and interpret the optimal models more profoundly. Along with the new local findings, this study delivered two significant general findings for cause-and-effect ML implementations in process industries. First, multi-perspective model comparison is vital for selecting a truly reliable model for interpretation. Second, adopting an accurate and granular interpretation method can profit both model comparison and interpretation.(3) (Paper III) A novel workflow was proposed to identify the accountable operational factors for boiler failures at WtE plants. In addition to data preprocessing and domain knowledge integration, it mainly comprised feature space embedding and unsupervised clustering. Two methods, PCA + K-means and Deep Embedding Clustering (DEC), were carried out and compared. The workflow succeeded in fulfilling the objective of a case study on three datasets from a WtE plant in Sweden, and DEC outperformed PCA + K-means for all the three datasets. DEC was superior due to its unique mechanism in which the embedding module and K-means are trained simultaneously and iteratively with the bidirectional information pass.(4) (Paper IV) A two-level (data structure level and algorithm mechanism level) workflow was put forward to detect imperceptible anomalies in energy consumption profiles of commercial buildings. The workflow achieved two objectives – it precisely detected the contextual energy anomalies hidden behind the time variation in the case study; it investigated the combined influence of data structures and algorithm mechanisms on unsupervised anomaly detection for building energy consumption. The overall conclusion was that the contextualization resulted in a less skewed estimation of correlations between instances, and the algorithms with more local perspectives benefited more from the contextualization.
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| 4. |
- Jansson, Stina, 1975-
(författare)
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Thermal formation and chlorination of dioxins and dioxin-like compounds
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis contributes to an increased understanding of the formation of dioxins and dioxin-like compounds in combustion processes. Although emissions to air from waste incineration facilities have been greatly reduced by the use of efficient air pollution control measures, the resulting residues (ashes and filters) are highly toxic and are classified as hazardous waste. The main objective of the work underlying this thesis was to elucidate the formation and chlorination pathways of dioxins and dioxin-like compounds in waste combustion flue gases in the temperature range 640-200°C in a representative, well-controlled laboratory-scale reactor using artificial municipal solid waste. This could contribute to the reduction of harmful emissions to air and also reduce the toxicity of waste incineration residues, thus reducing or even eliminating the need for costly and potentially hazardous after-treatment. A comparison of four different quenching profiles showed that the formation of polychlorinated dibenzo-p-dioxins (PCDD) and dibenzofurans (PCDF) was rapid and mainly occurred in the 640-400°C temperature region, with high dependency on sufficient residence time within a specific temperature region. Prolonged residence time at high temperatures (450/460°C) reduced the PCDD yields, even at lower temperatures along the post-combustion zone. PCDD, PCDF and PCN (polychlorinated naphthalene) isomer distribution patterns indicated contributions from chlorophenol condensation as well as chlorination reactions for all three classes of compounds. The formation of PCDDs was largely influenced by chlorophenol condensation and to some extent by chlorination reactions. For the PCDFs, chlorine substitution adjacent to the oxygen bridges was unfavoured, as demonstrated by the notably lower abundance of 1,9-substituted congeners. This was supported by bidirectional orthogonal partial least squares (O2PLS) modelling. The variable with the greatest influence on the distribution of PCDD congeners was the relative free energy (RΔGf). The O2PLS models displayed distinct clusters, dividing most of the homologues into two or three sub-groups of congeners which seemed to correspond to the probability of origination from chlorophenol condensation. The effects of injection of aromatic structures into the flue gas differed for each class of compounds. Injection of naphthalene increased the formation of monochlorinated naphthalene but the remaining homologues appeared to be unaffected. This was probably due to insufficient residence time at temperatures necessary for further chlorination. Injected dibenzo-p-dioxin was decomposed, chlorinated and re-condensated into PCDDs and PCDFs, whereas injection of dibenzofuran and fluorene reduced the PCDD levels in the flue gas.
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| 5. |
- Jonsson, Sofia, 1973-
(författare)
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The influence of soil and contaminant properties on the efficiency of physical and chemical soil remediation methods
- 2009
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- A vast number of sites that have been contaminated by industrial activities have been identified worldwide. Many such sites now pose serious risks to humans and the environment. Given the large number of contaminated sites there is a great need for efficient, cost-effective remediation methods. Extensive research has therefore been focused on the development of such methods. However, the remediation of old industrial sites is challenging, for several reasons. One major problem is that organic contaminants become increasingly strongly sequestered as they persist in the soil matrix for a long period of time. This process is often referred to as ‘aging’, and leads to decreasing availability of the contaminants, which also affects the remediation efficiency. In the work underlying this thesis, the influence of soil and contaminant properties on the efficiency of various physical and chemical soil remediation methods was investigated. The investigated contaminants were polycyclic aromatic hydrocarbons (PAHs), polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs). Briefly, the results show that as the size of soil particles decreases the contaminants become more strongly sorbed to the soil’s matrix, probably due to the accompanying increases in specific surface area. This affected the efficiency of the removal of organic pollutants by both a process based on solvent washing and processes based on chemical oxidation. The sorption strength is also affected by the hydrophobicity of the contaminants. However, for a number of the investigated PAHs their chemical reactivity was found to be of greater importance for the degradation efficiency. Further, the organic content of a soil is often regarded as the most important soil parameter for adsorption of hydrophobic compounds. In these studies the effect of this parameter was found to be particularly pronounced for the oxidation of low molecular weight PAHs, but larger PAHs were strongly adsorbed even at low levels of organic matter. However, for these PAHs the degradation efficiency was positively correlated to the amount of degraded organic matter, probably due to the organic matter being oxidized to smaller and less hydrophobic forms. The amount of organic matter in the soil had little effect on the removal efficiency obtained by the solvent-washing process. However, it had strong influence on the performance of a subsequent, granular activated carbon-based post-treatment of the washing liquid. In conclusion, the results in this thesis show that remediation of contaminated soils is a complex process, the efficiency of which will be affected by the soil matrix as well as the properties of the contaminants present at the site. However, by acquiring thorough knowledge of the parameters affecting the treatability of a soil it is possible to select appropriate remediation methods, and optimize them in terms of both remediation efficiency and costs for site- and contaminant-specific applications.
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| 6. |
- Larsson, Malin, 1981-
(författare)
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Computational methods for analyzing dioxin-like compounds and identifying potential aryl hydrocarbon receptor ligands : multivariate studies based on human and rodent in vitro data
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDD/Fs) and polychlorinated biphenyls (PCBs) are omnipresent and persistent environmental pollutants. In particular, 29 congeners are of special concern, and these are usually referred to as dioxin-like compounds (DLCs). In the European Union, the risks associated with DLCs in food products are estimated by a weighted sum of the DLCs’ concentrations. These weights, also called toxic equivalency factors (TEFs), compare the DLCs’ potencies to the most toxic congener, 2,3,7,8-tetrachloro-dibenzo-p-dioxin (2378- TCDD). The toxicological effects of PCDD/Fs and PCBs are diverse, ranging from chloracne and immunological effects in humans to severe weight loss, thymic atrophy, hepatotoxicity, immunotoxicity, endocrine disruption, and carcinogenesis in rodents.Here, the molecular structures of DLCs were used as the basis to study the congeneric differences in in vitro data from both human and rodent cell responses related to the aryl hydrocarbon receptor (AhR). Based on molecular orbital densities and partial charges, we developed new ways to describe DLCs, which proved to be useful in quantitative structure-activity relationship modeling. This thesis also provides a new approach, the calculation of the consensus toxicity factor (CTF), to condense information from a battery of screening tests. The current TEFs used to estimate the risk of DLCs in food are primarily based on in vivo information from rat and mouse experiments. Our CTFs, based on human cell responses, show clear differences compared to the current TEFs. For instance, the CTF of 23478-PeCDF is as high as the CTF for 2378-TCDD, and the CTF of PCB 126 is 30 times lower than the corresponding TEF. Both of these DLCs are common congeners in fish in the Baltic Sea. Due to the severe effects of DLCs and their impact on environmental and human health, it is crucial to determine if other compounds have similar effects. To find such compounds, we developed a virtual screening protocol and applied it to a set of 6,445 industrial chemicals. This protocol included a presumed 3D representation of AhR and the structural and chemical properties of known AhR ligands. This screening resulted in a priority list of 28 chemicals that we identified as potential AhR ligands.
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| 7. |
- Lindeberg, Carola, 1975-
(författare)
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Long-term changes of mercury, lead and persistent organic pollutants in arctic environments
- 2007
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The Arctic represents a huge area with poor infrastructure contributing to limited possibilities to establish monitoring and research programs. From the investigations that have been performed we know that the arctic environment is affected by anthropogenic emissions from lower latitudes, but knowledge about underlying transport processes, the arctic pollution extent and the rates of changes are limited. This is of particular concern since we are facing climate changes that will not only influence the pole-ward transport of pollutants, but also change conditions for the already accumulated pollutants in the arctic environment. In this thesis lake sediments and soil samples are used to study sub-arctic and arctic time trends and loads of PCBs, PBDE, pesticides, mercury and lead. The study sites are the area around Kangerlussuaq, located in western Greenland, and the Swedish mountains. The temporal trends for PCBs (69 congeners), PBDE (#47) and two pesticides (chlordane and hexachlorobenzene) are studied in seven surface lake sediment cores from Greenland. The concentrations of these persistent organic pollutants are one to two orders of magnitude lower compared to lake sediments from lower latitudes, but with temporal trends following emission and usage trends at lower altitudes, i.e., decreasing trends for PCBs, increasing for PBDE and no specific trends for the pesticides. A delayed deposition of the low-chlorinated PCBs compared to the high-chlorinated PCBs may support the hypothesis of ‘cold condensation’ and ‘global fractionation’ i.e., volatile compounds are fractionated during the pole-ward transport. For lead the concentration in three Greenland lake sediments is about 10 times lower than in sediments from industrial regions, but the past 200 years’ temporal trends follow emission trends in industrial regions. The mercury concentration and enrichment following the Industrial Revolution in the mid 19th century are in three lake sediments from Greenland and in twelve lake sediments from the Swedish mountains comparable with those in sediments from industrial regions; a result of the long atmospheric residence-time for mercury, making it a global pollution. Recently decreased mercury emissions in North America and Europe give declining concentrations in the sediment surfaces, especially in lakes located in the Swedish mountains. In Greenland deeper sediment cores, spanning the last 8000 years, there are substantial fluctuations in mercury concentration and stable lead isotopes (206Pb/207Pb). These fluctuations are the result of variations in deposition to the lake of aeolian material, driven by past variations in arctic climate. In surface soil the mercury concentrations and inventories from the Swedish mountains are 1.5-2 times higher than in soils from Greenland, but for both regions the concentrations are below the critical concentration set up by UN-ECE to protect the terrestrial ecosystem. No indications for mercury enrichment in colder areas, as suggested by the hypothesis of ‘cold condensation’, or in coastal areas, as suggested by the hypothesis of ‘mercury depletion events’, were observed. The highly minerogenic surface soils in sub-arctic and arctic regions have reduced capacity to store mercury, compared to boreal soils.
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| 8. |
- Lundin, Lisa, 1976-
(författare)
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Formation and degradation of PCDD/F in waste incineration ashes
- 2007
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The disposal of combustible wastes by incineration is a controversial issue that is strongly debated by both scientists and environmental activists due to the resulting emissions of noxious compounds, including (inter alia) polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs), heavy metals and acid gases like sulfur dioxide. Currently available air pollution control devices are capable of effectively cleaning flue gases, and PCDD/F emissions to air from modern municipal solid waste (MSW) incinerators are low. However, the PCDD and PCDF end up in ash fractions that, in Sweden, are usually deposited in landfills. The European Union has recently set a maximum permitted total concentration of 15 µg TEQ/kg for PCDD/F species in waste. Fly ash from municipal solid waste (MSW) incineration containing PCDD/Fs at concentrations above this limit will have to be remediated to avoid disposing of them in landfills; an expensive and environmentally unfriendly option. Therefore, effective, reliable and cost-effective methods for degrading PCDD/F in fly ash are required, and a better understanding of the behavior of PCDDs and PCDFs during thermal treatment will be needed to develop them. In the studies this thesis is based upon both the formation and degradation of PCDDs and PCDFs in ashes from MSW incineration were studied. The main findings of the investigations regarding PCCD/F formation were: - The concentrations of PCDD and PCDF in fly ash increased with reductions in the temperature in the post-combustion zone. - The homologue profile in the ash changed when the temperature in the post-combustion zone changed. - The final amounts of PCDD and PCDF present were affected by their rates of both formation and degradation, and the mechanisms involved differ between PCDDs and PCDFs. The main findings from the degradation studies were: - The chemical composition of ash has a major impact on the degradation potential of PCDD and PCDF. - The presence of oxygen during thermal treatment can enhance the degradation of PCDD and PCDF. - Thermal treatment is a viable option for degrading PCDD and PCDF in ashes from MSW. - Shifts in chlorination degree occur during thermal treatment. - Rapid heat transfer into the ash is a key factor for ensuring fast degradation of PCDD and PCDF. - Degradation of other chlorinated organic compounds, e.g. PCB and HCB, also occurs during thermal treatment of ash. - Reductions in levels of PCDD and PCDF were not solely due to their desorption to the gas phase. - Differences between the behavior of 2378-substituted congeners of PCDD and PCDF and the other congeners during thermal treatment were observed. - Differences in isomer patterns of both PCDD and PCDF were observed between the ash and gas phases after thermal treatment at both 300 and 500 oC. Overall, the results show that the formation and degradation mechanisms of PCDDs differ substantially from those of PCDFs. Thus these groups of compounds should be separately considered in attempts to identify ways to reduce their concentrations.
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| 9. |
- Ragnvaldsson, Daniel, 1976-
(författare)
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Hazard screening of contaminated sites : bioavailable fractions and biological in vitro tools
- 2007
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The environmental bioavailability of contaminants, rather than their total concentrations in the soil compartment play a decisive role for the risks associated with contaminated sites. Various soil constituents and abiotic conditions have strong influence on bioavailability, which may vary substantially between different locations. It is therefore necessary to site-specifically use tools that reflect the fractions of contaminants that are available to biota and pose the highest potential environmental risks. Bioassays provide integrated toxic responses which include effects from unknown contaminants or combinatory toxic effects from mixtures of contaminants. Thus, biological effect data greatly contribute to establish more realistic exposure and risk-scenarios at contaminated sites. The work underlying this thesis presents possible techniques for high capacity screening for site-specific hazards at contaminated areas. By combining rapid water extractions and cell-based in vitro designs measures of the toxic potential in soils was obtained. Toxicologically bioavailable fractions of mixed metal pollution, including arsenic, were primarily investigated in this thesis. In two of the studies, environmental availability and toxicological bioavailability of arsenic was explored in CCA-contaminated soils. Application of cell-based in vitro screening techniques was also conducted at a metal contaminated industrial site to obtain spatial distribution of toxicity. Multivariate association techniques were employed in the interpretation of environmental exposure and cytotoxicity data. It was shown that cell-based in vitro systems for both basal cytotoxicity and specific end-points targeting arsenic could assess the toxic potential from extracts obtained by several water-based extraction techniques including Pressurised Liquid Extraction (PLE). The cell-based in vitro systems were found to add important information on the site-specific differences in arsenics genotoxic potential from CCA-contaminated soils. The results highlight the importance of taking speciation and toxicological bioavailability into account in the risk analysis, rather than to base risk estimates on total load of contaminants. The presented screening approach was successfully applied at a metal polluted industrial site where spatial distribution of toxicity was obtained. PLE extraction also provided means for combined toxicological and chemical screening of explosives in soils from live-fire training ranges. Multivariate association techniques highly facilitated the interpretation of complex environmental data. The PLE was found to be a rapid extraction technique that has sufficient environmental relevance to be used in environmental impact analyses. It was also concluded that other cell-based in vitro systems that target specific toxic effects have large potential for being used in screening for a variety of environmental chemicals. Keywords: Environmental availability, Environmental bioavailability, Toxicological bioavailability, mixture toxicity, hazard screening, contaminated soils, heavy metals, arsenic, CCA, explosives, soil extraction, water extracts, cell-based in vitro tests, cytotoxicity, genotoxicity, PLE, MVDA, PCA, PLS.
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| 10. |
- Rattfelt Nyholm, Jenny, 1975-
(författare)
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Persistency, bioaccumulation and toxicity assessment of selected brominated flame retardants
- 2009
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Brominated flame retardants (BFRs) are chemicals used in e.g. electronic equipment, textiles and plastics for the prevention of fire. Over recent decades, concern has been raised regarding some heavily used BFRs, since the levels in the environment have been increasing. In the present thesis, persistent, bioaccumulative, and toxic (PBT) properties were studied for a structurally varied set of BFRs selected to represent more than 60 organic BFRs. The studied BFRs include: 2,4,4'-tribromodiphenyl ether (BDE 28), 2,2',3,4,4',5',6-heptabromodiphenyl ether (BDE 183), decabromodiphenyl ether (BDE 209), hexabromocyclododecane (HBCD), tetrabromobisphenol A (TBBPA), tetrabromobisphenol A 2-hydroxyethyl ether (TBBPA OHEE), 2,4,6-tribromophenol (246BrPh), 1,2-dibromo-4-(1,2-dibromoethyl)cyclohexane (TBECH), and hexabromobenzene (HxBrBz).It is likely that soil will act as a sink for BFRs. Therefore, studies of BFRs were performed on persistence in soil, and on bioaccumulation from soil in the earthworm Eisenia fetida. Large variation in the biodegradability in soil among the tested BFRs was observed. The studied brominated diphenyl ethers (BDE 28 and BDE 209) were very persistent under both aerobic and anaerobic conditions, while 246BrPh and TBECH degraded quickly in both aerobic and anaerobic soil. The bioaccumulation in earthworm from soil was high for HxBrBz, TBECH and for tested brominated diphenyl ethers with 4-6 bromine atoms (BDE 47, BDE 99, and BDE 153). Bioaccumulation was also studied in zebrafish after dietary exposure to a mixture of BFRs. It was shown that several metabolites were formed and retained in zebrafish, which highlights the importance of also searching for and identifying persistent degradation products. Maternal transfer was shown for all BFRs present in the female zebrafish. This shows that zebrafish young (fry) are exposed to these BFRs at approximately the same concentrations as female zebrafish during the early-life stages, when fish are usually most sensitive to organic contaminants. Toxicity of individual BFRs and a BFR mixture was studied in Nitocra spinipes using a silica gel-based system. Highest toxicities were observed for BDE 28, TBBPA, and TBBPA OHEE. In the mixture toxicity study, simultaneous exposure to low concentrations (individually causing no significant effect) of six BFRs significantly affected the survival of Nitocra spinipes. The results from the PBT studies presented in the thesis and literature data were compared with the criteria for PBT classification, as set in the European REACH legislation. Further, some BFRs with physico-chemical properties similar to those of identified PBTs were suggested to be prioritized for future PBT testing.
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